The primary objective of this controlled clinical study is to evaluate the clinical effect of decontamination of the implant surface during the surgical treatment of peri-implantitis using a 2% chlorhexidine solution or a 0.12% chlorhexidine solution. The secondary objective is to assess the microbiological effect of decontamination of the implant surface during the surgical treatment of peri-implantitis using a 2% chlorhexidine solution or a 0.12% chlorhexidine solution.